Process for obtaining diesel fuels from tars



Patented Sept. 2, 1941 ares r oric PBQCESS FQR OBTAINING DIESEL FUELS FROM TABS- No Drawing; Application December 21, 1939, Serial No. 310,410. In Germany August 8, 1935 3 Claims. (Ci. 196-13) This application is a continuation-in-part of my pending application Serial No. 94,291, filed August 4, 1936, now Patent No. 2,188,015, dated January 23, 1940, and relates to a process for obtaining Diesel fuels from tars such as lignite tar, shale tar, peat tar and the like. According to this invention it has been found that rich yields in Diesel fuels of excellent ignitibility are obtained if said tars are treated with selective solvents and the raffinite is subjected to cracking under suitable conditions.

Preferably the procedure may be carried out as follows:

The raw tar is topped, conveniently after centrifuging off the mechanical impurities, and advantageously two fractions are taken off, one fraction boiling up to about 200-220 0., a further fraction boiling up to about 260 C.

The further treatment of the topped tar aims at the manufacture of an intermediate product free from. all those special tar components, such as phenols, other acid oils, unsaturated and sulphur compounds of unknown nature, which interfere with the refining and the production of finished materials from lignite tars, shale tars and peat tars and the'like, in contradistinction to that'of petroleum or naphtha. For this purpose,

the topped tar (about 85% of the crude tar) is treated at a temperature of about 5060 C. or higher with phenol, preferably that obtained by topping of the tar, the phenol being employed in a quantity of 100% or more, calculated on the topped tar. Instead of phenol, cresol, or a mixture of phenols, as obtained from the tops, 1. e. fraction removed by primary distillation of the tar may be used. If the tar is readily soluble and therefore no substantial formation of layers takes place, the phenols are first diluted with water or the like. It may also be suitable to carry out the extraction after an addition of thinning oils up to 100% calculated on the distillation residue used. In case of such dilution, the temperature of treatment may be reduced, for instance down to about 30 C.

By the process described above, a refined prodnot or rafiin'ite is Obtained which, after removal of the phenols and of the thinning agent, if such is employed, considerably differs as to its chemical composition from the tar used as starting material, and which has a petroleum-like character.

It may be profitable to remove the paralnn wax from the tar before the latter is treated with selective solvents. In this case, the treatment with the phenols may be carried out at a temperature below 20 C.

If the process is carried out in the manner described above a very pure rafiinate, i. e. a raffinate freed from 0-, S- and N-compounds and asphalticsubstances i obtained as well as an extract practically free from paraffins.

It has now been found that the rafiiniteis particularly suitable as starting material for thermic cracking processes, and that if the conditions of' the cracking step are chosen in such a manner that gas oil accumulates as the cracking product in the main fraction, it is possible to obtain a'Diesel fuel satisfying all requirements.

For the cracking process, the raifinate may be used either direct or after having dewaxed the raffinate. In the latter case, it is suitable to recombine the oil running off during the sweating treatment with the main quantity-of the raffinate. The cracking process maybe carried out in the liquid or in the vapor phase, and pressure may be applied, if desired. In every case, the rafi'inate showed a remarkable cracking ability with very little inclination to form coke, thereby resulting in an increased. capacity of the plant.

Thereby it becomes necessary lessfrequently to shut. down the plant for the purpose of. cleaning it. Furthermore, it becomes possible by the uniformity of the material obtained by the pretreatment according to the invention, to select the optimal cracking conditions, and more particularly to maintain increased cracking temperatures without the danger of increased formation of gas and coke. This again leads to an acceleration of the, cracking process and an increase of the quantity passing through, thus obtaining altogether a considerable increase in the output of the cracking plant.

The fact that deposition of coke is avoided, is specially of benefit with cracking processes operating in the presence of catalysts. The regeneration of such catalysts when employing the raffinates of the present procedure becomes necessary only after a long use. For instance, it was found that when using ligmte tar oil obtained by distillation, twice the quantity of contact substance (activated coal) was required for the recovery of the same quantity of light oil as when using the present process. In addition thereto, the yield in percentage in the latter case was at least double the quantity as in the case of cracking the distillate.

A special advantage of the pretreating of lignite tars and the like with selective solvents like phenols, when transforming the tars into lighter hydrocarbons, also lies in the fact that the walls of the apparatus used are not at all or merely slightly attacked, where as the corresponding action of the unrefined tar is very detrimental.

The superiority of the present process is particularly evident, however, from the properties of the Diesel fuels obtained. As known, many difficulties are encountered when using lignite tar oils as Diesel fuels, especially for non-stationary engines, on account of its smell, its pretty unfavorable combustion effect when injected directly, and on account of its ageing tendency. According to the invention, however, namely by refining lignite tar and the like by means of selective solvents like phenol, and subsequent careful cracking of the rafiinate, it becomes possible, without distillation, which only means loss of time and is disadvantageous in regard to the quality of the fuel, to produce immediately from tar highly qualified Diesel fuels. These fuels are distinguished by a light color which does not change in storage, by an unobjectionable smell, high Ceten values, i. e. good ignitibility and by a soft burning off, and do not lead to formation of coke in the engine, or of deposits. They can also unhesitatingly be mixed with petroleum gas oils and synthetic Diesel oils.

The new process furthermore shows a way to subject onlyftliose parts of lignite tar and the like to a thermic conversion, which are suitable for this purpose, namely the fractions boiling at higher temperatures. A direct cracking of the topped lignite tar, i. e. without pretreating it according to the invention, would lead within a short time to an interruption of the cracking, due to strong formation of asphalt and coke, especially in the tubes. This would, make it necessary to dilute the tar, whenever using it, with lightoils, which, however, on the one hand would reduce the output of the plant, and on the other hand would incur gasification losses.

If however, as described above, the topping is effected up to about, 260, a starting material, particularly suitable for a continuous cracking free from disturbances, is obtained from the topping residue after refining, which is made more advantageous by the topping, and further quantities of suitable fuels can be gained from the distillate.

For example, operations are carried out in such a manner that of the fractions obtained while topping the tar, the lighter fraction boiling up to about 200 to 220 is decreosoted. In this process a phenol accumulates, which may be used in the selective treatment of the tar, and a light oil which, on account of its aromatic character,

forms a knock-proof fuel. The second fraction,-

that is to say the fraction boiling up to about 260, may be used as a Diesel fuel. It may however, be considerably improved for this purpose by treating it with selective solvents, for example by means of liquid sulphuric acid. It is, of course, possible, particularly whendealing with tars which are poor in easily boiling parts, to obtain in the topping step the entire first runnings in one fraction, and to use the latter as Diesel fuel, if necessary afterrafination.

The extracts obtained in the method described may be utilized in different ways after removing the phenols used as solvents by distilling or blowing off with steam. Among other purposes, they are suited for the manufacture of motor fuels free from knocking, by cracking or still better by hydrogenation under pressure, if it is not pre-- ferred to render applicable the tarry components contained in the extracts for road pavement.

Naturally the cracking of the rafiinate may also be conducted in such a manner, that a larger quantity of benzine-like fractions accumulate, which, due to their advantageous composition, form a suitable knock-proof fuel for benzine engines.

From the cracking or hydrogenation products respectively, the fractions suitable as a fuel are separated in a per se known manner by distillation or fractional condensation following immediately the thermic conversion process, and may be combined with each other, as well as with the topping fractions.

I claim:

1. Process for obtaining valuable Diesel fuels from paraifin containing tar from solid carbonaceous material which comprises topping said tar to remove constituents boiling below about 260 deg. C., subjecting the residue from said topping to treatment with a selective solvent which forms an extract portion containing in solution tarry components of the said residue and a raffinate portion which contains paraifin, separating the extract portion and the raiiinate portion produced by said treatment, filtering said rafiinate phase at about 20 deg. C. to separate crude paraf fin wax, and cracking the oil thus obtained.

2. Process for obtaining valuable Diesel fuels from paraffin containing tar from solid carbonaceous material which comprises topping said tar to remove constituents boiling below about 260 deg. C., subjecting the residue from said topping to treatment with a phenol of low boiling point which forms an extract portion containing in solution tarry components of the said residue and a rafiinate portion which contains parafiin, separating the extract portion and the raffinate portion produced by said treatment, filtering said rafiinate phase at about 20 deg C. to separate crude paraifin wax, and cracking the oil thus obtained.

3. Process for obtaining valuable Diesel fuels from parafiin containing tar from solid carbonaceous material which comprises topping said tar to remove constituents boiling below about 260 deg. 0., subjecting the residue from said topping to treatment with a selective solvent which forms an extract portion containing in solution tarry components of the said residue and a raffinate portion which contains paraffin, separating the extract portion and the rafiinate portion produced by said treatment, filtering said ramnate phase at about 20 deg. C. to separate crude paraffin wax, and cracking the oil thus obtained in the presence of catalysts.

FRIEDRICH SCHICK. 

